1. Field of the Invention
The invention relates to electronic driving devices, and particularly to a device for driving a light source module such as discharge lamps of a liquid crystal display (LCD) panel.
2. Related Art
Conventionally, discharge lamps such as cold cathode fluorescent lights (CCFLs) have been used as light sources for liquid crystal display (LCD) panels, and must be driven by high voltages. With larger LCD panels requiring a plurality of lamps, to achieve sufficient light intensity.
FIG. 3 is a conventional driving device for driving a light source module. The conventional driving device includes a switch circuit 10, a transformer circuit 11, a light source module 12, a feedback circuit 13, and a PWM controller 14. The switch circuit 10 converts a received direct current (DC) power signal to an alternating current (AC) signal. The transformer circuit 11 transforms the AC signal to an appropriate signal to drive the light source module 12. The feedback circuit 13 is connected between the light source module 12 and the PWM controller 14, for feeding back current flowing through the light source module 12 to the PWM controller 14. The PWM controller 14 controls the AC signal output from the switch circuit 10 based on the current output from the feedback circuit 13.
The feedback current is received from the light source module 12, and is sent to the driving device via an external circuit, thereby increasing the cost of an electronic device using the driving device.
FIG. 4 is another conventional driving device for driving a light source module. The driving device in FIG. 4 is substantially the same as that of FIG. 3, except that the feedback circuit 23 is connected between the transformer circuit 21 and the PWM controller 24, and the feedback current is received from the transformer circuit 21. Therefore, the feedback current is directly sent to the PWM controller 24 in the driving device without the need of the external circuit, and thus, costs of an electronic using the driving device can be reduced. However, the feedback current received from the transformer circuit 21 is unstable, and precision of the feedback current is deteriorated.